Electrolysis solution for electrolytic capacitor, and electrolytic capacitor

ABSTRACT

Provided is an electrolysis solution for an electrolytic capacitor, having high spark voltage and excellent electric conductivity and heat resistance to spark voltage, and an electrolytic capacitor using the electrolysis solution. An electrolysis solution for an electrolytic capacitor including at least a silicone-based surfactant, colloidal silica, an electrolyte salt, and an organic solvent, and an electrolytic capacitor using the electrolysis solution. Containing the silicone-based surfactant makes it possible to prevent charge balance of the colloidal silica from being lost.

TECHNICAL FIELD

The present invention relates to an electrolysis solution for anelectrolytic capacitor, having high spark voltage and excellent electricconductivity and heat resistance to spark voltage, and further relatesto an electrolytic capacitor using the electrolysis solution.

BACKGROUND ART

Conventionally, an electrolysis solution for an electrolytic capacitorobtained by dissolving organic acid, inorganic acid, or salts thereof asan electrolyte in an organic solvent has been used.

Among electrolysis solutions, development of an electrolysis solutionfor an electrolytic capacitor, which has high electric conductivity andspark voltage, has been carried out actively because electricconductivity is directly related to loss in an electrolytic capacitor,impedance properties, and the like.

As disclosed in Patent Literature 1, as additives for improving sparkvoltage, for example, sulfamic acid, suberic acid, dodecyl phosphate,porous polyimide, and the like are known. All of these additives haveexcellent initial spark voltage but soon deteriorate during use, andtherefore have a problem of poor heat resistance.

Patent Literature 2 discloses technology in which spark voltage isimproved by using colloidal silica as inorganic oxidized colloidalparticles in order to improve spark voltage while high electricconductivity is maintained. While an electrolysis solution containingcolloidal silica has high initial spark voltage, the electrolysissolution has a problem in that it gels during use and short-circuits andthus has poor heat resistance.

As mentioned above, an electrolysis solution for an electrolyticcapacitor having high spark voltage and excellent electric conductivityand heat resistance to spark voltage, and an electrolytic capacitorusing the electrolysis solution, have been demanded.

PRIOR ART Patent Literatures

[Patent Literature 1] Japanese Unexamined Patent Application,Publication No. 2009-283581

[Patent Literature 2] Japanese Unexamined Patent Application,Publication No. H05-6839

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide an electrolysissolution for an electrolytic capacitor having high spark voltage andexcellent electric conductivity and heat resistance to spark voltage,and an electrolytic capacitor using the electrolysis solution.

Solution to Problem

The present invention provides an electrolysis solution for anelectrolytic capacitor including at least a silicone surfactant,colloidal silica, an electrolyte salt, and an organic solvent, and anelectrolytic capacitor using the electrolysis solution.

That it so say, the present invention provides the following.

A first invention is an electrolysis solution for an electrolyticcapacitor, including at least a silicone surfactant, colloidal silica,an electrolyte salt, and an organic solvent.

A second invention is the electrolysis solution for an electrolyticcapacitor as defined in the first invention, wherein a ratio by mass ofthe silicone surfactant to the colloidal silica is 0.01 to 10.

A third invention is the electrolysis solution for an electrolyticcapacitor as defined in the first or second invention, wherein thesilicone surfactant is polyether-modified silicone.

A fourth invention is the electrolysis solution for an electrolyticcapacitor as defined in the third invention, wherein thepolyether-modified silicone is a pendant-type polymer or an ABA-typepolymer.

A fifth invention is the electrolysis solution for an electrolyticcapacitor as defined in any one of the first to fourth inventions,wherein a content of the silicone surfactant in the electrolysissolution for an electrolytic capacitor is 0.01 to 20 mass %.

A sixth invention is the electrolysis solution for an electrolyticcapacitor as defined in any one of the first to fifth inventions,wherein the electrolyte salt is any one of compounds represented bygeneral formulae (1) to (5):

(wherein in the formulae (1) to (5), groups R¹ to R²⁵ representhydrogen, an alkyl group having 1 to 18 carbon atoms, an alkoxy grouphaving 1 to 18 carbon atoms, or a hydroxyl group, which may be the sameas or different from each other; adjacent groups among R¹ to R²⁵ may belinked together to form an alkylene group having 2 to 6 carbon atoms;and X⁻ represents a carboxylic acid anion or a boron compound anion).

A seventh invention is the electrolysis solution for an electrolyticcapacitor as defined in any one of the first to sixth inventions,further including a defoaming agent containing at least one selectedfrom the group consisting of an acetylene compound and polyglycol.

An eighth invention is an electrolytic capacitor using an electrolysissolution for an electrolytic capacitor as defined in the first toseventh inventions.

Advantageous Effects of Invention

The present invention can achieve an electrolysis solution for anelectrolytic capacitor having high spark voltage, excellent electricconductivity and heat resistance to spark voltage, as well as anelectrolytic capacitor using the electrolysis solution.

DESCRIPTION OF EMBODIMENTS

An electrolysis solution for an electrolytic capacitor in accordancewith the present invention will be described.

The present inventors have extensively studied and have found that theabove-mentioned problem can be solved by an electrolysis solution for anelectrolytic capacitor including at least a silicone surfactant,colloidal silica, an electrolyte salt, and an organic solvent, as wellas an electrolytic capacitor using the electrolysis solution, and havecompleted the present invention.

<Silicone Surfactant>

A silicone surfactant includes a compound having a siloxane bond(Si—O—Si) as a main skeleton and also has a Si—C bond. Specific examplesof the silicone surfactant include dimethyl silicone, methyl phenylsilicone, chlorophenyl silicone, alkyl-modified silicone,fluorine-modified silicone, amino-modified silicone, alcohol-modifiedsilicone, phenol-modified silicone, carboxy-modified silicone,epoxy-modified silicone, fatty acid ester-modified silicone,polyether-modified silicone, and the like.

The molecular weight of the silicone surfactant is preferably, forexample, 100 to 100000. Use of a silicone surfactant having a molecularweight in this range can prevent charge balance of the colloidal silicafrom being lost. Consequently, gelation does not occur for a long periodof time. Therefore, an electrolysis solution for an electrolyticcapacitor having high spark voltage and excellent heat resistance can beobtained.

The alkyl-modified silicone is a modified silicone having an alkyl grouphaving 6 or more carbon atoms, a 2-phenyl propyl group, or the like. Thealcohol-modified silicone is a modified silicone having an alcoholichydroxyl group. The epoxy-modified silicone is a modified siliconehaving a glycidyl group, an alicyclic epoxy group, or the like. Theamino-modified silicone is a modified silicone having an amino groupsuch as an amino propyl group and an N-(2-aminoethyl)aminopropyl group.The fatty acid ester silicone is a modified silicone having an estergroup of fatty acid. The polyether-modified silicone is a modifiedsilicone having a polyoxy alkylene group (for example, a polyoxyethylene group, a polyoxypropylene group, a polyoxyethylene oxypropylenegroup, and the like).

The silicone surfactant can be used singly or in combination of two ormore thereof. Among them, from the viewpoint that gelation of theelectrolysis solution is prevented, polyether-modified silicone isparticularly preferable.

Examples of the polyether-modified silicone include a pendant-typepolymer, an ABA-type polymer, an (AB)_(n)-type polymer, a branched typepolymer, and the like. Among them, a pendant-type polymer or an ABA-typepolymer is preferable.

The pendant type is typically a compound represented by general formula(A), and the ABA type is typically a compound represented by generalformula (B).

In the compounds represented by the above-mentioned general formulae (A)and (B), R_(A) or R_(B) represents an alkyl group having 1 to 20 carbonatoms; Y or Z represents a hydrogen atom or an alkyl group having 1 to10 carbon atoms; m represents an integer of 0 to 1000; n or P representsan integer of 1 to 1000; and a, b, c, and d each independentlyrepresents an integer of 0 to 100.

Y or Z represents a hydrogen atom or an alkyl group having 1 to 10carbon atoms. Preferably, Y or Z represents a hydrogen atom from theviewpoint of dispersibility.

<Electrolyte Salt>

An electrolyte salt used in the present invention may be any salt thatis usually used in an electrolytic capacitor. Among the electrolytesalts, any of the compounds represented by the following generalformulae (1) to (5) are preferably used as the electrolyte salt.

In the general formulae (1) to (5), groups R¹ to R²⁵ represent hydrogen,an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to18 carbon atoms, or a hydroxyl group, which may be the same as ordifferent from each other; adjacent groups among R¹ to R²⁵ may be linkedtogether to form an alkylene group having 2 to 6 carbon atoms; and X⁻represents a carboxylic acid anion or a boron compound anion.

Specific examples of a cation moiety of the compound represented by thegeneral formula (1) include ammonium cations; quaternary ammoniumcations such as a tetramethylammonium cation, a tetraethyl ammoniumcation, a tetrapropyl ammonium cation, a tetraisopropyl ammonium cation,a tetrabutyl ammonium cation, a trimethyl ethyl ammonium cation, atriethyl methyl ammonium cation, a dimethyl diethyl ammonium cation, adimethyl ethyl methoxy ethyl ammonium cation, a dimethyl ethyl methoxymethyl ammonium cation, a dimethyl ethyl ethoxy ethyl ammonium cation, atrimethyl propyl ammonium cation, a dimethyl ethyl propyl ammoniumcation, a triethyl propyl ammonium cation, a spiro-(1,1′)-pyrrolidiniumcation, a piperidine-1-spiro-1′-pyrrolidinium cation, and aspiro-(1,1′)-bipiperidinium cation; tertiary ammonium cations such as atrimethylamine cation, a triethylamine cation, a tripropylamine cation,a triisopropyl amine cation, a tributylamine cation, a diethyl methylamine cation, a dimethyl ethyl amine cation, a diethyl methoxy aminecation, a dimethyl methoxy amine cation, a dimethyl ethoxy amine cation,a diethyl ethoxy amine cation, a methyl ethyl methoxy amine cation, anN-methyl pyrrolidine cation, an N-ethyl pyrrolidine cation, an N-propylpyrrolidine cation, an N-isopropyl pyrrolidine cation, an N-butylpyrrolidine cation, an N-methyl piperidine cation, an N-ethyl piperidinecation, an N-propyl piperidine cation, an N-isopropyl piperidine cation,and an N-butyl piperidine cation; secondary ammonium cations such as adimethylamine cation, a diethylamine cation, a diisopropylamine cation,a dipropylamine cation, a dibutylamine cation, a methyl ethyl aminecation, a methyl propyl amine cation, a methyl isopropyl amine cation, amethylbutyl amine cation, an ethyl isopropyl amine cation, an ethylpropyl amine cation, an ethyl butyl amine cation, an isopropyl butylamine cation, and a pyrrolidine cation; and the like.

Among them, an ammonium cation, a tetraethyl ammonium cation, a triethylmethyl ammonium cation, a spiro-(1,1′)-pyrrolidinium cation, an N-methylpyrrolidine cation, a dimethyl ethyl amine cation, a diethyl methylamine cation, a trimethylamine cation, a triethylamine cation, adiethylamine cation, and the like, are preferably used because they havean excellent effect of improving the spark voltage and/or the electricconductivity, and improving heat resistance.

Specific examples of the cation moiety of the compound represented bythe general formula (2) include a tetramethyl imidazolium cation, atetraethyl imidazolium cation, a tetrapropyl imidazolium cation, atetraisopropyl imidazolium cation, a tetrabutyl imidazolium cation, a1,3-dimethyl imidazolium cation, a 1,3-diethyl imidazolium cation, a1,3-dipropyl imidazolium cation, a 1,3-diisopropyl imidazolium cation, a1,3-dibutyl imidazolium cation, a 1-methyl-3-ethyl imidazolium cation, a1-ethyl-3-methyl imidazolium cation, a 1-butyl-3-methyl imidazoliumcation, a 1-butyl-3-ethyl imidazolium cation, a 1,2,3-trimethylimidazolium cation, a 1,2,3-triethyl imidazolium cation, a1,2,3-tripropyl imidazolium cation, a 1,2,3-triisopropyl imidazoliumcation, a 1,2,3-tirbutyl imidazolium cation, a 1,3-dimethyl-2-ethylimidazolium cation, a 1,2-dimethyl-3-ethyl imidazolium cation, and thelike. Among them, a tetramethyl imidazolium cation, a tetraethylimidazolium cation, a 1,3-dimethyl imidazolium cation, a 1,3-diethylimidazolium cation, a 1-ethyl-3-methyl imidazolium cation, and the like,are preferably used because they have high electric conductivity andexcellent improvement effect of heat resistance.

Specific examples of a cation moiety of the compound represented by thegeneral formula (3) include a tetramethyl imidazolinium cation, atetraethyl imidazolinium cation, a tetrapropyl imidazolinium cation, atetraisopropyl imidazolinium cation, a tetrabutyl imidazolinium cation,a 1,3,4-trimethyl-2-ethyl imidazolinium cation, a1,3-dimethyl-2,4-diethyl imidazolinium cation, a1,2-dimethyl-3,4-diethyl imidazolinium cation, a 1-methyl-2,3,4-triethylimidazolinium cation, a 1,2,3-trimethyl imidazolinium cation, a1,2,3-triethyl imidazolinium cation, a 1,2,3-tripropyl imidazoliniumcation, a 1,2,3-triisopropyl imidazolinium cation, a 1,2,3-tributylimidazolinium cation, a 1,3-dimethyl-2-ethyl imidazolinium cation, a1-ethyl-2,3-dimethyl imidazolinium cation, a 4-cyano-1,2,3-trimethylimidazolinium cation, a 3-cyanomethyl-1,2-dimethyl imidazolinium cation,a 2-cyanomethyl-1,3-dimethyl imidazolinium cation, a4-acetyl-1,2,3-trimethyl imidazolinium cation, a 3-acetylmethyl-1,2-dimethyl imidazolinium cation, a 4-methylcarboxymethyl-1,2,3-trimethyl imidazolinium cation, a 3-methylcarboxymethyl-1,2-dimethyl imidazolinium cation, a4-methoxy-1,2,3-trimethyl imidazolinium cation, a 3-methoxymethyl-1,2-dimethyl imidazolinium cation, a 4-formyl-1,2,3-trimethylimidazolinium cation, a 3-formyl methyl-1,2-dimethyl imidazoliniumcation, a 3-hydroxyethyl-1,2-dimethyl imidazolinium cation,4-hydroxymethyl-1,2,3-trimethyl imidazolinium cation, a2-hydroxyethyl-1,3-dimethyl imidazolinium cation, and the like. Amongthem, a tetramethyl imidazolinium cation, a tetraethyl imidazoliniumcation, a 1,2,3-trimethyl imidazolinium cation, a 1,2,3-triethylimidazolinium cation, and a 1-ethyl-3-methyl imidazolinium cation arepreferably used because they have high electric conductivity and areexcellent in improvement effect of heat resistance.

Specific examples of a cation moiety of the compound represented by thegeneral formula (4) include a tetramethyl pyrazolium cation, atetraethyl pyrazolium cation, a tetrapropyl pyrazolium cation, atetraisopropyl pyrazolium cation, a tetrabutyl pyrazolium cation, a1,2-dimethyl pyrazolium cation, a 1-methyl-2-ethyl pyrazolium cation, a1,2-diethyl pyrazolium cation, a 1,2-dipropyl pyrazolium cation, a1,2-dibutyl pyrazolium cation, a 1-methyl-2-propyl pyrazolium cation, a1-methyl-2-butyl pyrazolium cation, a 1-methyl-2-hexyl pyrazoliumcation, a 1-methyl-2-octyl pyrazolium cation, a 1-methyl-2-dodecylpyrazolium cation, a 1,2,3-trimethyl pyrazolium cation, a 1,2,3-triethylpyrazolium cation, a 1,2,3-tripropyl pyrazolium cation, a1,2,3-triisopropyl pyrazolium cation, a 1,2,3-tributyl pyrazoliumcation, a 1-ethyl-2,3,5-trimethyl pyrazolium cation, a1-ethyl-3-methoxy-2,5-dimethyl pyrazolium cation, a3-phenyl-1,2,5-trimethyl pyrazolium cation, a3-methoxy-5-phenyl-1-ethyl-2-ethyl pyrazolium cation, a1,2-tetramethylene-3,5-dimethyl pyrazolium cation, a1,2-tetramethylene-3-phenyl-5-methyl pyrazolium cation, a1,2-tetramethylene-3-methoxy-5-methyl pyrazolium cation, and the like.Among them, tetramethyl pyrazolium cation, a tetraethyl pyrazoliumcation, a 1,2-dimethyl pyrazolium cation, a 1,2-diethyl pyrazoliumcation, a 1-methyl-2-ethyl pyrazolium cation, because they have highelectric conductivity and are excellent in improvement effect of heatresistance.

Specific examples of a cation moiety of the compound represented by thegeneral formula (5) include an N-methyl pyridinium cation, an N-ethylpyridinium cation, an N-propyl pyridinium cation, an N-isopropylpyridinium cation, an N-butyl pyridinium cation, an N-hexyl pyridiniumcation, an N-octyl pyridinium cation, an N-dodecyl pyridinium cation, anN-methyl-3-methyl pyridinium cation, an N-ethyl-3-methyl pyridiniumcation, an N-propyl-3-methyl pyridinium cation, an N-butyl-3-methylpyridinium cation, an N-butyl-4-methyl pyridinium cation, anN-butyl-4-ethyl pyridinium cation, and the like. Among them, an N-methylpyridinium cation, an N-ethyl pyridinium cation, an N-butyl pyridiniumcation, an N-butyl-3-methyl pyridinium cation, and the like, becausethey have high electric conductivity and are excellent in improvementeffect of heat resistance.

Anion X⁻ to be combined with the above-mentioned cation is a carboxylicacid anion or a boron compound anion. The carboxylic acid anion is ananion of organic carboxylic acid such as aromatic carboxylic acid andaliphatic carboxylic acid. The organic carboxylic acid may have asubstituent group. Specific examples of the carboxylic acid anioninclude aromatic carboxylic acid anions such as a phthalic acid anion, asalicylic acid anion, an isophthalic acid anion, a terephthalic acidanion, a trimellitic acid anion, a pyromellitic acid anion, a benzoicacid anion, a resorcylic acid, a cinnamic acid anion, a naphthoic acidanion, and a mandelic acid anion; aliphatic carboxylic acid anionsincluding saturated carboxylic acid anions such as an oxalic acid anion,a malonic acid anion, a succinic acid anion, a glutaric acid anion, anadipic acid anion, a pimelic acid anion, suberic acid anion, an azelaicacid anion, a sebacic acid anion, an undecanoic diacid anion, adodecanoic diacid anion, a tridecanoic diacid anion, a tetradecanoicdiacid anion, a pentadecanoic diacid anion, a hexadecanoic diacid anion,a 3-tert-butyl adipic acid anion, a methyl malonic acid anion, an ethylmalonic acid anion, a propyl malonic acid anion, a butyl malonic acidanion, a pentyl malonic acid anion, a hexyl malonic acid anion, adimethyl malonic acid anion, a diethyl malonic acid anion, a methylpropyl malonic acid anion, a methylbutyl malonic acid anion, an ethylpropyl malonic acid anion, a dipropyl malonic acid anion, a methylsuccinic acid anion, an ethyl succinic acid anion, a 2,2-dimethylsuccinic acid anion, a 2,3-dimethyl succinic acid anion, a 2-methylglutaric acid anion, a 3-methyl glutaric acid anion, a 3-methyl-3-ethylglutaric acid anion, a 3,3-diethyl glutaric acid anion, a methylsuccinic acid anion, a 2-methyl glutaric acid anion, a 3-methyl glutaricacid anion, a 3,3-dimethyl glutaric acid anion, a 3-methyl adipic acidanion, a 1,6-decanedicarboxylic acid anion, a 5,6-decanedicarboxylicacid anion, a formic acid anion, an acetic acid anion, a propionic acidanion, butyric acid anion, an isobutyric acid anion, a valeric acidanion, a caproic acid anion, an enanthic acid anion, a caprylic acidanion, a pelargonic acid anion, a laurylic acid anion, a myristic acidanion, a stearic acid anion, a behenic acid anion, an undecanoic acidanion, a boric acid anion, a borodiglycolic acid anion, a borodioxalicacid anion, a borodisalicylic acid anion, a borodiazelaic acid anion, aborodilactic acid, an itaconic acid anion, a tartaric acid anion, aglycolic acid anion, a lactic acid anion, and a pyruvic acid anion, andaliphatic carboxylic acid anions containing an unsaturated carboxylicacid such as a maleic acid anion, a fumaric acid anion, an acrylic acidanion, a methacrylic acid anion, and an oleic acid anion. These may beused singly or in combination of two or more thereof. Among them, aphthalic acid anion, a maleic acid anion, a salicylic acid anion, abenzoic acid anion, an adipic acid anion, a sebacic acid anion, anazelaic acid anion, a 1,6-decanedicarboxylic acid anion, a 3-tert-butyladipic acid anion, and the like, are preferable because they have theimproved spark voltage and are thermally stable.

Examples of the boron compound anion include a boric acid anion, aborodiazelaic acid anion, a borodisalicylic acid anion, a borodiglycolicacid anion, a borodilactic acid anion, a borodioxalic acid anion, andthe like. Among them, a boric acid anion, a borodisalicylic acid anion,a borodiglycolic acid anion, and the like, are preferably used becausethey are excellent in the spark voltage.

Among the above-mentioned anions, in the case where they are used forlow-voltage/middle-voltage electrolytic capacitor, a phthalic acidanion, a maleic acid anion, a salicylic acid anion, a benzoic acidanion, an adipic acid anion, a borodisalicylic acid anion, aborodiglycolic acid anion, and the like, are preferably used. Thus, highelectric conductivity and excellent heat resistance are obtained. On theother hand, in use for a high-voltage electrolytic capacitor, a sebacicacid anion, an azelaic acid anion, a 1,6-decanedicarboxylic acid anion,a 3-tert-butyl adipic acid anion, a boric acid anion, a borodisalicylicacid anion, a borodiglycolic acid anion, and the like, are preferablyused. Thus, excellent effect can be obtained in terms of the sparkvoltage and heat resistance.

In the compounds represented by the above-mentioned general formulae (1)to (5), the compounds represented by the general formulae (1) to (3) arepreferably used because they are stable for a long period of time, canachieve high spark voltage, and are excellent in heat resistance.Specific examples of the electrolyte salts to be used forlow-voltage/middle voltage electrolytic capacitors includedimethylethylamine maleate, dimethylethylamine phthalate,tetraethylammonium maleate, tetraethylammonium phthalate, trimethylaminemaleate, trimethylamine phthalate, triethylamine maleate, triethylaminephthalate, diethylamine maleate, diethylamine phthalate,spiro-(1,1′)-bipyrrolidinium maleate, spiro-(1,1′)-bipyrrolidiniumphthalate, 1-ethyl-3-methyl imidazolium maleate, 1-ethyl-3-methylimidazolium phthalate, 1-ethyl-3-methyl imidazolinium maleate,1-ethyl-3-methyl imidazolinium phthalate, tetramethyl imidazoliumphthalate, tetramethyl imidazolinium phthalate, tetraethyl imidazoliumphthalate, tetraethyl imidazolinium phthalate, and the like. On theother hand, examples of the electrolyte salts to be used forhigh-voltage electrolytic capacitors include dimethylamine sebacate,diethylamine sebacate, trimethylamine sebacate, triethylamine sebacate,ammonium sebacate, dimethylamine azelate, diethylamine azelate,trimethylamine azelate, triethylamine azelate, ammonium azelate,ammonium 1,6-decanedicarboxylate, dimethylamine 1,6-decanedicarboxylate,diethylamine 1,6-decanedicarboxylate, trimethylamine1,6-decanedicarboxylate, triethylamine 1,6-decanedicarboxylate, N-methylpyrrolidine borodisalicylate, and the like.

The content of electrolyte salt in the electrolysis solution for anelectrolytic capacitor is preferably 1.0 to 60 mass %, more preferably5.0 to 50 mass %, and particularly preferably 10 to 40 mass %.

A content of less than 1.0 mass % has the problem that sufficientelectrical characteristic cannot be obtained, and the content of morethan 60 mass % has the problem that the specific resistance isincreased.

<Colloidal Silica>

The colloidal silica is a colloid of SiO₂ or hydrate thereof, which hasa particle diameter of 1 to 300 nm and which does not have a certainstructure. The colloidal silica can be obtained by allowing dilutehydrochloric acid to act on silicate, followed by carrying out dialysis.The smaller the particle diameter is, the more easily gelation proceeds.However, the larger the particle diameter is, the less easily gelationoccurs. The particle diameter of the colloidal silica used in thepresent invention is preferably 10 to 50 nm, and more preferably 10 to30 nm. When the colloidal silica having the particle diameter in thisrange is used, gelation does not easily occur, and a stable dispersionstate can be maintained even when the electrolytic capacitor is used.

The colloidal silica is hardly dissolves in water or an organic solvent.In general, the colloidal silica is dispersed in an appropriatedispersive medium to form a colloid liquid, and the colloid liquid isadded to an electrolysis solution. Thus, the colloidal silica can beused in a dispersion state even when the electrolytic capacitor is used.

The colloidal silica used in the present invention may besodium-stabilized type colloidal silica, or acidic colloidal silica, orammonium-stabilized type colloidal silica.

In the sodium-stabilized type colloidal silica, the surface of colloidalsilica is an ONa group. In the acidic colloidal silica, the surface ofcolloidal silica is an OH group from which Na has been removed. In theammonium stabilized type colloidal silica, Na has been removed to forman OH group, and then ammonium is added for stabilization.

Among them, acidic colloidal silica or ammonium-stabilized typecolloidal silica having less content of sodium ion is preferred.

The content of the colloidal silica in the electrolysis solution for anelectrolytic capacitor is 0.1 to 20 mass %, more preferably 0.2 to 15mass %, and particularly preferably 0.3 to 10 mass %. The content ofless than 0.1 mass % has a problem that improvement effect of theelectrical characteristic in an electrolytic capacitor is small, and thecontent of more than 20 mass % has a problem in that viscosity is largeto thus make handling difficult.

An average particle diameter of the colloidal silica is not particularlylimited, and it is preferably 1 to 100 nm, more preferably 10 to 50 nm,and particularly preferably 10 to 30 nm. When the colloidal silica hasthe above-mentioned average particle diameter, it is possible to obtainan electrolysis solution for an electrolytic capacitor having excellentdispersibility in a solvent.

The shape of the colloidal silica may be any one of a sphere, a chainshape, an annular shape in which the colloidal silica is aggregated inan annular shape and dispersed in a solvent.

<Organic Solvent>

As an organic solvent used for an electrolysis solution for anelectrolytic capacitor, a protic polar solvent or an aprotic polarsolvent can be used. The solvent may be used singly or in combinationtwo or more solvents.

Examples of the protic polar solvent include monohydric alcohols(methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol,cyclopentanol, cyclohexanol benzyl alcohol, and the like), andpolyvalent alcohols and oxyalcohol compounds (such as ethylene glycol,propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve,methoxypropylene glycol, dimethoxy propanol, and the like).

Examples of the aprotic polar solvent include γ-butyrolactone,γ-valerolactone, amide (for example, N-methylformamide,N,N-dimethylformamide, N-ethyl formamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethyl acetamide, N-ethyl acetamide, N,N-diethylacetamide, and hexamethylphosphoric amide); sulfolane (for example,sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane); chainsulfones (for example, dimethyl sulfone, ethyl methyl sulfone, and ethylisopropyl sulfone), cyclic amides (for example, N-methyl-2-pyrrolidone);carbonates (for example, ethylene carbonate, propylene carbonate, andisobutylene carbonate); nitriles (for example, acetonitrile); sulfoxides(for example, dimethyl sulfoxide); 2-imidazolidinones [for example,1,3-dialkyl-2-imidazolidinone (for example,1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, and1,3-di(n-propyl)-2-imidazolidinone); and1,3,4-trialkyl-2-imidazolidinone (for example,1,3,4-trimethyl-2-imidazolidinone)], and the like.

When the solvent is used for low-voltage/middle-voltage electrolyticcapacitors, a solvent including γ-butyrolactone as a main solvent ispreferably used. Furthermore, the content of water contained in theelectrolysis solution for an electrolytic capacitor is preferablysmaller. When the solvent is used for high voltage electrolyticcapacitor, ethylene glycol is preferable. Furthermore, the content ofwater contained in the electrolysis solution for an electrolyticcapacitor is not particularly limited but it is preferably 0.1 to 30mass %, and more preferably 0.5 to 20 mass %. This amount of waterenables excellent electric conductivity to be obtained.

The content of the silicone surfactant contained in the electrolysissolution for an electrolytic capacitor is preferably 0.01 to 20 mass %,more preferably 0.05 to 15 mass %, and particularly preferably 0.1 to 10mass %. When the content is less than 0.01 mass %, an effect ofpreventing aggregation of colloidal silica cannot sufficiently beobtained. When the content is more than 20 mass %, the electricconductivity in the electrolysis solution may be somewhat reduced.

The content ratio (ratio by mass) of the colloidal silica to thesilicone surfactant in the electrolysis solution for an electrolyticcapacitor may be any ratio by mass, but preferably the content ratio ofthe colloidal silica to the silicone surfactant is preferably 1:0.01 to10, more preferably 1:0.05 to 5.0, and particularly preferably 1:0.1 to2.0. The content ratio is set at this range, it is possible to preventthe electrolysis solution from being gelled, so that more excellent heatresistance can be achieved.

When the silicone surfactant is contained in the electrolysis solutionfor an electrolytic capacitor, it is possible to prevent gelation causedby colloidal silica at the time of heating, storage, or use. Thus, it ispossible to maintain excellent electric conductivity and spark voltagefor a long period of time.

<Defoaming Agent>

According to the present invention, the electrolysis solution for anelectrolytic capacitor may contain a defoaming agent. Any defoamingagents capable of suppressing foaming of an electrolysis solution with asilicone surfactant added can be used. Specific examples of thedefoaming agent containing an acetylene compound include SURFYNOL 104E,DF-75, and MD-20, OLFIN E1004, E1010, E1020, PD-001, PD-002W, PD-004,PD-005, EXP4001, EXP4200, EXP4123, EXP4300, WE-003, P-10PG, AF-103, andSK-14, all of which are manufactured by Nissin Chemical Co., Ltd;examples of a defoaming agent containing polyglycol include BYK-018,BYK-021, BYK-022, BYK-024, BYK-028, BYK-093, and BYK-1730, all of whichare manufactured by BYK-Chemie; SN Defoamer 170, 260, manufactured bySAN NOPCO, and the like.

When the defoaming agent contains the electrolysis solution for anelectrolytic capacitor, a part of foam of the silicone surfactant isreplaced by a defoaming agent so as to prevent generation of foam.Consequently, when an electrolytic capacitor is impregnated with anelectrolysis solution, the electrolysis solution can be uniformly placedinto the further inner side of a separator. Therefore, when theelectrolytic capacitor is operated, colloidal silica can act moreuniformly by electrode foil, and an electrolytic capacitor having higherwithstand voltage can be manufactured.

The content ratio (ratio by mass) of the silicone surfactant to thedefoaming agent in the electrolysis solution for an electrolyticcapacitor may be an arbitrary ratio by mass, but the ratio of thesilicone surfactant to the defoaming agent is preferably 1:0.001 to 3.0,more preferably 1:0.005 to 1.5, and particularly preferably 1:0.01 to0.5.

The content of a defoaming agent in the electrolysis solution for anelectrolytic capacitor is preferably 0.001 to 10 mass %, and morepreferably 0.01 to 5 mass %.

<Other Additives>

The electrolysis solution for an electrolytic capacitor of the presentinvention may contain additives other than the above. Examples of suchadditives include polyvinyl alcohol, phosphoric acid compounds such asdibutyl phosphoric acid and phosphorous acid; boron compounds such asboric acid, Mannit, a complex of boric acid with Mannit or Sorbit, acomplex of boric acid with polyhydric alcohol such as ethylene glycoland glycerin; and nitro compounds such as o-nitrobenzoic acid,m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol,p-nitrophenol, and the like.

An addition amount is preferably 0.1 to 10 mass %, and more preferably0.5 to 5.0 mass %. The addition amount of less than 0.1 mass % has aproblem that sufficient spark voltage cannot be obtained. The additionamount of more than 10 mass % has a problem that electric conductivityis reduced.

<Electrolytic Capacitor>

The electrolytic capacitor of the present invention contains theabove-mentioned electrolysis solution for an electrolytic capacitor.

An electrolytic capacitor of the present invention is described taken analuminum electrolytic capacitor as an example. The aluminum electrolyticcapacitor is an electrolytic capacitor formed by using a chemicalconversion foil formed as a dielectric body as an oxide coating bysubjecting the surface of aluminum foil to anodic oxidation treatmentfor the anode side electrode, and disposing a cathode side electrode toface the anode side electrode with a separator interposed therebetween,and allowing an electrolysis solution to be held therein.

As performance required for an electrolysis solution formiddle-voltage/low-voltage electrolytic capacitors, the electricconductivity after heat resistance test (105° C., 2000 hours) ispreferably 7.0 mS/cm or more, more preferably 7.3 mS/cm or more, furthermore preferably 7.7 mS/cm or more, and particularly preferably 8 mS/cmor more. The spark voltage after the heat resistance test (105° C., 2000hours) is preferably 200 V or more, more preferably 205 V or more,further more preferably 210 V or more, and particularly preferably 215 Vor more. As performance required for a middle-voltage/low-voltageelectrolytic capacitor, the withstand voltage is preferably 200 V ormore, more preferably 210 V or more, further more preferably 220 V ormore, further preferably 230 V or more, and particularly preferably 250V or more. The withstand voltage can be measured by the measurementmethod described in Examples, for example.

As performance required for an electrolysis solution for a high-voltageelectrolytic capacitor, the electric conductivity after heat resistancetest (105° C., 2000 hours) is preferably 2.0 mS/cm or more, morepreferably 2.3 mS/cm or more, further more preferably 2.7 mS/cm or more,and particularly preferably 3 mS/cm or more. The spark voltage after theheat resistance test (105° C., 2000 hours) is preferably 550 V or more,more preferably 555 V or more, further more preferably 560 V or more,and particularly preferably 565 V or more. As performance required for ahigh-voltage electrolytic capacitor, the withstand voltage is preferably550 V or more, more preferably 560 V or more, further more preferably570 V or more, further preferably 580 V or more, and particularlypreferably 595 V or more. The withstand voltage can be obtained by themeasurement method described in Examples, for example.

In general, an electrolytic capacitor using an electrolysis solutioncontaining an electrolyte salt and colloidal silica is excellent in theinitial spark voltage, but has the problem that performance maydeteriorate. The cause of deterioration of the spark voltage is becauseelectric charge balance of the colloidal silica is lost due tocontaining of electrolyte salt, and then the colloidal silica isaggregated or/and polymerized when the electrolytic capacitor is used.As a result, an electrolysis solution is gelled, thus deteriorating heatresistance.

When a silicone surfactant to be used in the present invention iscontained, it is possible to prevent the electric charge balance of thecolloidal silica from being lost, and aggregation does not easily occur.Consequently, gelation can be prevented. As a result, it is possible toproduce an electrolysis solution for an electrolytic capacitor, which isexcellent in initial spark voltage and has excellent electricconductivity and excellent heat resistance in spark voltage, and anelectrolytic capacitor using the electrolysis solution.

EXAMPLES

Hereinafter, the present invention will be described by Examples. Itshould not be construed that the present invention is not limited toExamples. The term “part” denotes “part by mass” and “%” denotes “mass%.”

Examples 1 to 15 and Comparative Examples 1 to 7

Firstly, production examples of middle-voltage/low-voltage electrolyticcapacitor and an electrolysis solution used for the electrolyticcapacitor are described.

166 parts of phthalic acid and 530 parts of γ-butyrolactone as a solventwere mixed and stirred while 73.1 parts of N,N-dimethyl ethyl amine wasdropped so as to obtain a dimethylethylamine phthalate solution. Then,40.0 parts of colloidal silica (Snowtex N-40, manufactured by NissanChemical Industries, Ltd., aqueous dispersion, solid content: 40%,average particle diameter: 20 to 30 nm, pH 9.0 to 10), and thebelow-mentioned surfactant and/or a defoaming agent were added to theabove-obtained solution and mixed thereof. Then the mixture wasconcentrated at 80° C. to obtain an electrolysis solution for anelectrolytic capacitor.

Types and amounts of surfactant and defoaming agent used in each Exampleand Comparative Example are described in the following. Numeric valuesin parentheses show the ratio by mass of the surfactant normalized whenthe mass of the colloidal silica (solid content) is defined as 1, andthe ratio by mass of the defoaming agent normalized when the mass of thesurfactant is defined as 1.

Details of the additives and defoaming agents are as follows.

“pendant-type”=polyether-modified silicone (pendant-type): “SilwetL-7657” manufactured by Momentive, molecular weight: 5000

“ABA type”=polyether-modified silicone (ABA type): “Silwet L-8500”manufactured by Momentive, molecular weight: 2800

“amino modified”=amino-modified silicone: “XF42-B1989” manufactured byMomentive, molecular weight: 20000

“alcohol modified”=alcohol-modified silicone: “XF3905” manufactured byMomentive, molecular weight: 25000

sodium hexametaphosphate: manufactured by ALDRICH

polyethylene glycol (molecular weight: 600): manufactured by Wako PureChemical Industries, Ltd.

polyethylene oxide (molecular weight: 100000): manufactured by Wako PureChemical Industries, Ltd.

“BYK”: polyglycol-containing defoaming agent, “BYK-024” manufactured byBYK-Chemie;

Defoaming agent Surfactant (ratio by mass) (ratio by mass) Ex. 1:pendant-type (0.01) not contained Ex. 2: pendant-type (0.05) notcontained Ex. 3: pendant-type (0.1) not contained Ex. 4: pendant-type(0.5) not contained Ex. 5: pendant-type (1.0) not contained Ex. 6:pendant-type (2.0) not contained Ex. 7: pendant-type (3.0) not containedEx. 8: pendant-type (5.0) not contained Ex. 9: pendant-type (8.0) notcontained Ex. 10: pendant-type (10.0) not contained Ex. 11: pendant-type(11.0) not contained Ex. 12: ABA-type (0.5) not contained Ex. 13:amino-modified (0.5) not contained Ex. 14: alcohol-modified (0.5) notcontained Ex. 15: pendant-type (0.5) BYK (0.1) Co. Ex. 1*: not containednot contained Co. Ex. 2: not contained not contained Co. Ex. 3*:pendant-type (0.5) not contained Co. Ex. 4*: not contained BYK (0.1) Co.Ex. 5: sodium hexametaphosphate (0.5) not contained Co. Ex. 6:polyethylene glycol having a not contained molecular weight of 600 (0.5)Co. Ex. 7: polyethylene oxide having a not contained molecular weight of100000 (0.5) (Ex = Example, Co Ex = Comparative Example)

(*) In Comparative Examples 1, 3, and 4, colloidal silica was not added.In this case, the “additive amount” of the surfactant and the defoamingagent are represented by the ratio thereof to the amount of colloidalsilica assuming that the colloidal silica was added equally in theabove.

<Production of Electrolytic Capacitor>

Electrolytic capacitors were produced by using the above-mentionedelectrolysis solutions. Firstly, a capacitor element was formed bywinding an anode foil and a cathode foil with a separator interposedtherebetween. An anode tab and a cathode tab were connected to the anodefoil and the cathode foil, respectively. The anode tab and the cathodetab were made of aluminum with high purity, and formed of a flat portionconnected to each foil and a round-bar portion continuing to the flatportion. To the round-bar portion, anode lead wire and cathode lead wirewere connected. Note here that each foil and electrode tab was connectedby stitch.

The thus configured capacitor element was impregnated with each of theabove-mentioned electrolysis solutions for an electrolytic capacitor.The capacitor element impregnated with an electrolysis solution washoused in a bottomed cylindrical exterior case made of aluminum, sealingbody made of butyl rubber and having a through-hole for leading out alead wire into an opening end of the exterior case is inserted, followedby sealing the electrolytic capacitor by caulking the end portion of theexterior case so as to obtain an aluminum electrolytic capacitor.Specifications of aluminum electrolytic capacitor elements usingelectrolysis solutions of the above-mentioned Examples 1 to 15 andComparative Examples 1 to 7 include rated voltage of 250 V and ratedcapacitance of 47 μF.

The electrolysis solution for an electrolytic capacitor and theelectrolytic capacitor were evaluated as follows.

(Evaluation Method of Electric Conductivity)

In the evaluation method of the electric conductivity, electricconductivity of the electrolysis solution for an electrolytic capacitorat 30° C. was measured by using SC meter SC72 manufactured by YokogawaElectric Corporation. As the heat resistance, electric conductivity wasmeasured after 2000 hours has passed at a temperature of 105° C.

(Evaluation Method of Spark Voltage)

An evaluation method of spark voltage was carried out by applying aconstant current of 5 mA/cm² to an electrolysis solution for anelectrolytic capacitor at 25° C., and examining a voltage-time curve. Avoltage at which spark or scintillation was observed for the first timein the voltage ascending curve was defined as spark voltage (V). As theheat resistance, spark voltage was measured after 2000 hours has passedat a temperature of 105° C.

As for the electrolytic capacitor, electric current of 5 mA/cm² andvoltage of 350 V were respectively applied at a temperature of 105° C. Avalue of a voltage at which a spark or scintillation was observed forthe first time in the voltage-time ascending curve was recorded aswithstand voltage.

The measurement results of the above-mentioned evaluation in Examplesand Comparative Examples are summarized. The electric conductivity(mS/cm) and the spark voltage (V) were described in parentheses (initialvalue and value after 2000-hour test). Withstand voltages (V) wereresults of the above-mentioned tests in the electrolytic capacitor.

Electric conductivity Spark voltage (initial value and (initial valueand Withstand value after test) value after test) voltage Ex. 1: (8.1,7.6) (208, 206) 215 Ex. 2: (8.1, 7.9) (213, 212) 228 Ex. 3: (8.1, 8.1)(218, 218) 236 Ex. 4: (8.1, 8.1) (218, 218) 237 Ex. 5 (8.1, 8.1) (218,218) 238 Ex. 6: (8.1, 8.1) (218, 218) 237 Ex. 7: (8.1, 7.9) (214, 213)228 Ex. 8: (8.1, 7.8) (213, 212) 223 Ex. 9: (8.1, 7.6) (208, 206) 216Ex. 10: (8.1, 7.5) (208, 206) 214 Ex. 11: (8.1, 7.2) (204, 201) 205 Ex.12: (8.1, 8.1) (218, 218) 237 Ex. 13: (8.1, 7.9) (217, 215) 233 Ex. 14:(8.1, 7.9) (217, 215) 233 Ex. 15: (8.1, 8.1) (229, 229) 256 Co. Ex. 1:(8.1, 8.1) (100, 70)  60 Co. Ex. 2: (8.1, 4.1) (140, 85)  75 Co. Ex. 3:(8.1, 8.1) (105, 75)  65 Co. Ex. 4: (8.1, 8.1) (100, 70)  60 Co. Ex. 5:(6.7, 4.2) (125, 80)  78 Co. Ex. 6: (6.7, 4.1) (125, 80)  76 Co. Ex. 7:(6.8, 4.4) (122, 78)  74 (Ex = Example, Co Ex = Comparative Example)

Based on Comparative Example 1 which does not contain any of colloidalsilica, surfactant, and a defoaming agent, Comparative Example 2containing only colloidal silica, and Comparative Example 3 containingonly surfactant showed improvement of the spark voltage and thewithstand voltage to some extent. However, Example 4 containing both thecolloidal silica and the surfactant showed remarkable improvement of thespark voltage and the withstand voltage. Furthermore, also Example 15containing a defoaming agent showed further improvement of the sparkvoltage and the withstand voltage. This shows contrast to ComparativeExample 4, which does not contain colloidal silica and a surfactant butwhich contains a defoaming agent, does not show the improvement of thespark voltage and the withstand voltage.

Examples 16 to 30 and Comparative Examples 8 to 14

The below-mentioned production and evaluation methods are ones for ahigh-voltage electrolytic capacitor and an electrolysis solution for thesame.

188 parts (1.0 mol) of azelaic acid and 1630 parts of ethylene glycol assolvent were mixed and stirred, while 146 parts (2.0 mol) ofdiethylamine was dropped thereto so as to obtain a diethylamine azelatesolution in diethylamine ethylene glycol, 100 parts of colloidal silica(Snowtex N-40 manufactured by Nissan Chemical Industries, Ltd., aqueousdispersion, solid content: 40%, average particle diameter: 20 to 30 nm,pH 9.0 to 10), and the below-mentioned surfactant and/or defoaming agentwere added and mixed thereto, and then concentrated at 80° C. to obtainan electrolysis solution for an electrolytic capacitor.

Types and amounts of the surfactant and the defoaming agent used in eachExample and Comparative Example follow. Ways of description are the sameas mentioned above.

Defoaming agent Surfactant (ratio by mass) (ratio by mass) Ex. 16:pendant-type (0.01) not contained Ex. 17: pendant-type (0.05) notcontained Ex. 18: pendant-type (0.1) not contained Ex. 19: pendant-type(0.5) not contained Ex. 20: pendant-type (1.0) not contained Ex. 21:pendant-type (2.0) not contained Ex. 22: pendant-type (3.0) notcontained Ex. 23: pendant-type (5.0) not contained Ex. 24: pendant-type(8.0) not contained Ex. 25: pendant-type (10.0) not contained Ex. 26:pendant-type (11.0) not contained Ex. 27: ABA type (0.5) not containedEx. 28: amino-modified (0.5) not contained Ex. 29: alcohol-modified(0.5) not contained Ex. 30: pendant-type (0.5) BYK (0.1) Co. Ex. 8*: notcontained not contained Co. Ex. 9: not contained not contained Co. Ex.10*: pendant-type (0.5) not contained Co. Ex. 11*: not contained BYK(0.1) Co. Ex. 12: sodium hexametaphosphate (0.5) not contained Co. Ex.13: polyethylene glycol having a not contained molecular weight of 600(0.5) Co. Ex. 14: polyethylene oxide having a not contained molecularweight of 100000 (0.5) (Ex = Example, Co Ex = Comparative Example)

(*) In Comparative Examples 8, 10, and 11, colloidal silica was notadded. In this case, the “additive amount” of the surfactant and thedefoaming agent are represented by the ratio thereof to the amount ofcolloidal silica assuming that the colloidal silica was added equally inthe above.

<Production of Electrolytic Capacitor>

The aluminum electrolytic capacitor elements using the above-mentionedExamples 16 to 30 and Comparative Examples 8 to 17 were produced asmentioned above. Specifications of the aluminum electrolytic capacitorelement include rated voltage of 500 V and rated capacitance of 350 μF.

The electrolysis solution for an electrolytic capacitor and theelectrolytic capacitor were evaluated as follows.

The electric conductivity and the spark voltage were evaluated asmentioned above.

As for the electrolytic capacitor, electric current of 10 mA/cm² andvoltage of 700 V were respectively applied at a temperature of 105° C. Avalue of a voltage at which a spark or scintillation was observed forthe first time in the voltage-time ascending curve was recorded aswithstand voltage.

The measurement results of the above-mentioned evaluation in Examplesand Comparative Examples are summarized. The electric conductivity(mS/cm) and the spark voltage (V) were described in parentheses (initialvalue and value after 2000-hour test). Withstand voltages (V) wereresults of the above-mentioned tests in the electrolytic capacitor.

Electric conductivity Spark voltage (initial value and (initial valueand Withstand value after test) value after test) voltage Ex. 16: (3.2,2.6) (558, 555) 566 Ex. 17: (3.2, 2.9) (563, 561) 575 Ex. 18: (3.2, 3.2)(568, 568) 582 Ex. 19: (3.2, 3.2) (568, 568) 583 Ex. 20: (3.2, 3.2)(568, 568) 583 Ex. 21: (3.2, 3.2) (568, 568) 582 Ex. 22: (3.2, 2.9)(564, 562) 576 Ex. 23: (3.2, 2.8) (563, 561) 574 Ex. 24: (3.2, 2.6)(559, 556) 567 Ex. 25: (3.2, 2.4) (558, 555) 565 Ex. 26: (3.2, 2.2)(554, 550) 555 Ex. 27: (3.2, 3.2) (568, 568) 583 Ex. 28: (3.2, 3.1)(567, 565) 580 Ex. 29: (3.2, 3.1) (567, 565) 580 Ex. 30: (3.2, 3.2)(579, 579) 601 Co. Ex. 8: (3.2, 3.2) (400, 230) 230 Co. Ex. 9: (3.2,1.5) (420, 248) 250 Co. Ex. 10: (3.2, 3.2) (410, 240) 240 Co. Ex. 11:(3.2, 3.2) (400, 230) 230 Co. Ex. 12: (1.8, 0.8) (405, 234) 240 Co. Ex.13: (1.8, 0.8) (405, 234) 238 Co. Ex. 14: (1.7, 0.7) (400, 231) 235 (Ex= Example, Co Ex = Comparative Example)

Similar to the case of the above-mentioned middle-voltage/low-voltageelectrolytic capacitors, also in the case of high-voltage electrolyticcapacitors of Examples 16 to 30, Comparative Example 9 containing onlycolloidal silica, and Comparative Example 10 containing only surfactantshowed slight improvement of improvement of the spark voltage and thewithstand voltage with respect to Comparative Example 8 which does notcontain any of colloidal silica and surfactant. However, Example 19containing both the colloidal silica and the surfactant showedremarkable improvement of the spark voltage and the withstand voltage.In addition, also Example 30 containing a defoaming agent showed furtherimprovement of the spark voltage and the withstand voltage. This showscontrast to Comparative Example 11, which does not contain colloidalsilica and a surfactant but which contains a defoaming agent, does notshow the improvement of the spark voltage and the withstand voltage.

INDUSTRIAL APPLICABILITY

An electrolysis solution for an electrolytic capacitor in accordancewith the present invention has high spark voltage and excellent electricconductivity and heat resistance to spark voltage, and therefore can beapplicable in a wide variety of industries.

The invention claimed is:
 1. An electrolysis solution for anelectrolytic capacitor, comprising at least a silicone surfactant,colloidal silica, an electrolyte salt, and an organic solvent, wherein aratio by mass of the silicone surfactant to the colloidal silica is 0.01to
 10. 2. The electrolysis solution for an electrolytic capacitoraccording to claim 1, wherein the silicone surfactant ispolyether-modified silicone.
 3. The electrolysis solution for anelectrolytic capacitor according to claim 1, wherein the siliconesurfactant is polyether-modified silicone and is a pendant-type polymeror an ABA-type polymer.
 4. An electrolysis solution for an electrolyticcapacitor, comprising at least a silicone surfactant, colloidal silica,an electrolyte salt, and an organic solvent, wherein a content of thesilicone surfactant in the electrolysis solution for an electrolyticcapacitor is 0.01 to 20 mass %.
 5. An electrolysis solution for anelectrolytic capacitor, comprising at least a silicone surfactant,colloidal silica, an electrolyte salt, and an organic solvent, furthercomprising a defoaming agent containing at least one selected from thegroup consisting of an acetylene compound and polyglycol.
 6. Anelectrolytic capacitor comprising an electrolysis solution for anelectrolytic capacitor according to claim 1.